It's really looking at that older age group and how much prior immunity they have, either from previous infection or vaccination, that I think has been the best indicator so far of how severe a given number of cases is going to end up being in terms of hospitalizations and deaths.

Stephen Kissler

Every additional layer of protection that we get helps, and so I would highly recommend, especially somebody who's elderly who has yet gotten vaccinated to do so, because it really can go a long way towards giving you the durable and robust immunity that you want, this is definitely the time.

Stephen Kissler

I do still think it's a potential cause for concern that we may still see a higher case fatality rate and higher hospitalizations for Covid in United States than the UK because of the differences in underlying immunity.

Stephen Kissler